rwst_tryenter
if (rwst_tryenter(&vpvfsentry->ve_lock, RW_WRITER))
if (rwst_tryenter(&vpvfsentry->ve_lock, RW_READER))
if (rwst_tryenter(&vpvfsentry->ve_lock, RW_WRITER))
if (rwst_tryenter(&vpvfsentry->ve_lock, RW_READER))
extern int rwst_tryenter(rwstlock_t *, krw_t);